ok guys i need some help, ive been searching for awhile now and still cant figure this out! my car runs great all year long until winter time starts. around this time of the year is when i notice the cars backfire or hesitation problem. when im in 3rd or 4th gear and Im at wot, around 4500 to 5000 rpms the car backfires/hesitates pretty bad. my friend was driving behind me last night when this problem occured and he explained that it backfired and black smoke came out! after it does this the rpms will increase all the way to 7k normally

this started to happen when a shop here in Houston installed my greddy profec b spec 2 boost controller last year, after this happened i switched over to the ams mbc
but since it happened again last night i can tell the problem is still there
my car is an 06 mr, turbo back, fmic, lower ic pipe, and mbc, all from ams

any advise would be appreciated cause this sucks!!!

 

sounds like you might have more than one problem. boost spike and fuel cut and possibly clutch slip. whats the boost at? whats the car sound like? tuned? fuel pump?

 

boost is at 24 then tapers off to 20, car sounds normal no abnormal sounds are heard its just backfires or hesitates i do have a walbro 255 fuel pump in the car but this was occuring even with the stock fuel pump car has only has a mild tune due to my wideband not showing up yet cant really get an aggressive tune without the wideband

 

have you logged the car with Mitsulogger or Evoscan? Winter air might be allowing cat to make more power and introducing boost/fuel cut

 

Regap your plugs to .022. NGK only!

 

not to sure if i wanna swap spark plugs just cause they were changed a few months back and the car runs fine just with this winter air it starts to act up gonna roll the dice and start with another tune once my wideband shows up im kinda hoping this corrects the problem

 

You should go back to your tuner.

 

I have the same problem around the same rpm range, and already suspected the wheater, it occurs only when it's freezing as soon as temperature goes up to around 6 degrees & up i dont have the problem. I first suspected a faulty 255 pump since it is recently installed but it started when the outside temperature went down and only under wot, if i accelerate gradually it does'nt happen. I hope this explains it. I'll just have to be carefull and have the dealership log the car to be certain and see if they find anything. No control lights light up when it happens. just a pop in the exhaust a puff of black smoke and the hesitation for 2-3 times before it picks up again.

EVO VIII
ecutek
Injen intake
Invidia downpipe & catback
22-24psi

 

hey bro... Im in Houston also... and the recent temp drops to 30 degrees F caused my Evo9 to do the same thing. Its only when i hit WOT it will pop and keep popping for a bit and then its fine the rest of the way through, even the next up shifts are fine... its just that initial drop of the hammer... During warmer weather (60 degrees and up) its fine. My tune is good also as i have 30+ dyno runs to back it up showing 11.2 AFRs and i lay down 340whp on a mustang dyno. I recently suspected my Walbro 255 as a recent issue... due to noise and a recent weird AFR spike (leaning out) so im waiting for the new pump to come in... but i think the popping etc.. is just w/ the cold weather. I think it has something to do w/ the denser air making changes in load? Once i get the new pump in, im re-tuning myself to this colder weather and hope ones i dial it in... it will be good all year round. ( i was tuned in extremely hot weather earlier)

-Tom

 

your definitly going to increase load in colder weather, but shouldnt the stock computer be able to adjust for that? Also to OP your spark plugs can be damaged easily with a bad tune, pull the plug is it black?

 

This sounds like fuel cut to me. Load values increase with cold temps due to the denser air, and no the ECU doesn't correct for it very well ... especially if you have a MBC/EBC. Your solution would be to lower the boost or re-tune the car to handle the increased boost level (or at least raise the load value for fuel cut).

For the person who mentioned the hesitation when the car is spooling, that sounds like a knock issue. I'd suggest logging the vehicle and checking for knock in the 100 - 200 load area on spool up. The timing is fairly aggressive there.

 

I haven't got a tune on my car yet but I get this problem when it's cold outside. It started when I put on my tbe and intercooler pipes.

 

Tim, it's boost cut. The Evo's tolerance for overboost if somewhat low and the values in the ECU need to be modified or you can hit the cut in cold weather.

 

You should not be driving it hard before its tuned. When you change the VE of the engine the calibration will no longer be correct.

 

for my issue, its doing the pop during spool and its not knocking in that area. instead its knocking in the upper rpm (after the popping subsided) im going to start my own thread as to not hijack Jorge's, lol... fyi my load for boost cut is set at 315, which i thought turns it off... and i never hit above 280-290 load at max.